ppmtobmp(1)

1Ppmtobmp User Manual(0)                                Ppmtobmp User Manual(0)
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NAME

6       ppmtobmp - convert a PPM image into a BMP file
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SYNOPSIS

10       ppmtobmp
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12       [-windows]
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14       [-os2]
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16       [-bpp=bits_per_pixel]
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18       [-mapfile=filename]
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20       [ppmfile]
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22       Minimum  unique abbreviation of option is acceptable.  You may use dou‐
23       ble hyphens instead of single hyphen to denote options.   You  may  use
24       white space in place of the equals sign to separate an option name from
25       its value.
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DESCRIPTION

30       This program is part of Netpbm(1).
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32       ppmtobmp reads a PPM image as input and produces a Microsoft Windows or
33       OS/2 BMP file as output.
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OPTIONS

37       In  addition  to  the options common to all programs based on libnetpbm
38       (most notably -quiet, see
39        Common Options ⟨index.html#commonoptions⟩ ), ppmtobmp  recognizes  the
40       following command line options:
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44       -windows
45              Tells  the  program  to  produce  a  Microsoft Windows BMP file.
46              (This is the default.)
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49       -os2   Tells the program to produce an OS/2 BMP file.   (Before  August
50              2000, this was the default).
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53       -bpp   This tells how many bits per pixel you want the BMP file to con‐
54              tain.  Only 1, 4, 8, and 24 are possible.  By default,  ppmtobmp
55              chooses  the smallest number with which it can represent all the
56              colors in the input image.  If you specify a number too small to
57              represent  all the colors in the input image, ppmtobmp tells you
58              and terminates.  You can use pnmquant or ppmdither to reduce the
59              number of colors in the image.
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61              Before  Netpbm  10.85 (December 2018), ppmtobmp ignores this op‐
62              tion if the input is PBM and produces  a  BMP  with  1  bit  per
63              pixel.   With  these  versions,  if you want more than that, use
64              pbmtopgm to convert the PBM to PGM first.
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67       -mapfile=filename
68              This identifies a file to use as  the  BMP  palette  (aka  "col‐
69              ormap").   In  one BMP subformat, the BMP stream contains a pal‐
70              ette of up to 256 colors, and represents the image raster as in‐
71              dices  into that palette.  Normally, ppmtobmp takes care of com‐
72              puting a suitable palette, but if you are going to  dissect  the
73              BMP output in some way, you may want certain values for the pal‐
74              ette indices.  E.g. you might want red to be 13, where  ppmtobmp
75              would  (arbitrarily) choose 39.  In that case, you can construct
76              the palette yourself and use this option to tell ppmtobmp to use
77              your palette.
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79              This option does not control what colors are in the output.  The
80              colors in the output are exactly those in  the  input,  and  the
81              palette you supply must contain at least all the colors that are
82              in the input.  You can use pnmremap to adjust your  input  image
83              so that it contains only colors from your palette.
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85              The palette file is a Netpbm format file with one pixel per pal‐
86              ette entry.  Each pixel must have a distinct color (no repeats).
87              The  order of the BMP palette ppmtobmp generates is the order of
88              the pixels in the palette file, going from top to  bottom,  left
89              to right.
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91              A  BMP  palette may have at most 256 colors, so the palette file
92              must have at most 256 pixels.
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94              You may find pnmcolormap useful in generating the palette  file.
95              pamseq too.
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97              In  the  case  of grayscale image, if you are processing the BMP
98              image, it
99                may be convenient for you to have the actual  gray  values  in
100              the raster
101                part  of  the  image rather than arbitrary indices into a pal‐
102              ette.  There is
103                no BMP format specifically for that, but you can achieve it by
104              using a
105                palette  in  which  each  index  is  equal to the indexed gray
106              value, and then
107                ignoring the palette when you process the BMP image.
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109              Here is an example of doing that:
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112                  $ pamseq 1 255 > mapfile.pgm
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114                  $ ppmtobmp -mapfile=mapfile.pgm input.pgm > output.bmp
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118              This option was new in Netpbm 10.45 (December 2008).
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NOTES

125       To get a faithful reproduction of the input image, the  maxval  of  the
126       input  image  must  be 255.  If it is something else, the colors in the
127       BMP file may be slightly different from the colors in the input.
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129       Windows icons are not BMP files.  Use ppmtowinicon to create those.
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AUTHOR

138       Copyright (C) 1992 by David W. Sanderson.
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DOCUMENT SOURCE

141       This  manual  page was generated by the Netpbm tool 'makeman' from HTML
142       source.  The master documentation is at
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144              http://netpbm.sourceforge.net/doc/ppmtobmp.html
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146netpbm documentation           20 December 2018        Ppmtobmp User Manual(0)